Pneumatic tires are assembled on a building drum from unvulcanized rubber and fabric. The tires are then vulcanized in a metal mold to form the familiar shape of a finished tire. To facilitate the molding operation, the uncured or "green" tires are coated prior to molding with what is commonly referred to as an outside green tire paint.
The outside green tire paints serve the functions of allowing the rubber to slip as it comes in contact with the metal mold and the paints also serve as a release agent when at the end of the vulcanization cycle, the tire must separate from the mold. Another function of the paint is to provide air bleeding of air which becomes trapped between the tire and the mold. Outside green tire paints also aid in the appearance of the finished tire.
The outside green tire paints used heretofore are solvent based. That is they use a hydrocarbon solvent such as gasoline as a carrier. This hydrocarbon solvent when applied to the outside of a green tire will evaporate into the atmosphere thus leading to pollution of the atmosphere with organic vapors. Air scrubbing equipment would need to be installed to prevent air contamination with organic vapors. Also allowing the solvents to evaporate is a tremendous waste of our natural resources.
Another common ingredient in the prior art paints is silicone. Silicone is used to provide the slip needed when the tire slides into the mold. Silicone provides the required slip very well, however, it also can lead to tire defects. Splice areas where tire components are put together are especially vulnerable to interference by silicone. Two particular problem areas are the tread splice and the liner splice. If either of these splice areas have the slightest opening, silicone can become present in the opening and not allow the rubber to self-adhere during the vulcanizing process. U.S. Pat. No. 3,507,247 discloses a typical prior art outside green tire paint together with an apparatus for applying said paint. It would be desirable to have an outside green tire paint which was free of both hydrocarbon solvents and silicones.